"Triode and Single Ended Triode (SET) amps are popular for their warmer, fuller, and easy to settle into sound. But triode amps have limitations! Ultra-linear has more extension on the top and bottom, not to mention greater power. They have greater “pop” with a bigger difference between light and dark, and loud and soft. Having triode only is VERY limiting.
The best option is to have both triode and ultra-linear. PrimaLuna engineers in Holland designed an ingenious circuit that lets you change from triode to ultra-linear with a push of a button on the supplied remote control. "